This invention relates to methods of inhibiting diarrhea induced by Escherichia coli heat-stable enterotoxin and, more particularly, to such methods which involve the use of substantially nontoxic materials providing a source of sulfhydryl groups.
As is known, entertoxigenic Escherichia coli may produce a heat-labile toxin or a heat-stable toxin (ST). Both are important causes of diarrheal disease in humans and domestic animals. ST specifically activates the particulate fraction of guanylate cyclase in intestinal mucosal cells (Hughes et al., Clin. Res. 26:524A, 1978), resulting in increased mucosal cell cyclic guanosine monophosphate (GMP) levels and a net increase in intestinal fluid secretion (Hughes et al., Nature (London) 271: 755-756, 1978).
Although the precise regulation of guanylate cyclase activity and cyclic GMP accumulation in vivo are unknown, several studies suggest that free radicals activate guanylate cyclase and that guanylate cyclase activity is influenced by the oxidation-reduction state of the cell and by intracellular levels of thiols and disulfides (Brandwein et al., J. Biol. Chem., 256:2958-2962, 1981; Broughler et al., J. Biol. Chem., 254:12450-12454, 1979; Craven et al., Cancer Res., 37:4088-4097, 1977; Katsuki et al., J. Cyclic Nucleotide Res., 3:23-35, 1977; Mittal et al., Proc. Natl. Acad. Sci. U.S.A., 74:4360-4364, 1977; Murad et al., Adv. Cyclic Nucleotide Res., 11:175-204, 1979; and White et al., J. Biol. Chem., 251:7304-7312, 1976). Butylated hydroxyanisole, a free radical scavenger, significantly reduces both ST activation of guanylate cyclase and ST-induced intestinal fluid secretion (Guerrant et al., J. Infect. Dis., 142:220-228, 1980). Also, hydroxylamine, an agent that activates guanylate cyclase by the production of free radicals (Kimura et al., J. Biol. Chem., 250:8016-8022, 1975), causes intestinal ion transport alterations similar to those seen with ST (Field, Rev. Infect. Dis., 1:918-925, 1979). Recently, Brandwein et al., supra, demonstrated that the disulfide compound cystamine could almost completely inactivate a highly purified preparation of guanylate cyclase. These findings may relate to the mechanism of action of ST or, alternatively, that thiols or disulfides might alter binding of ST to its receptor or alter subsequent ST activation of particulate guanylate cyclase. Staples et al. (J. Biol. Chem., 255:4716-4721, 1980) have reported that their ST preparation lost activity on treatment with reducing agents.
There remains a need for a practical means for inhibiting diarrhea induced by Escherichia coli heat-stable enterotoxin.